U.S. patent number 5,592,969 [Application Number 08/401,944] was granted by the patent office on 1997-01-14 for turbulence arrester.
Invention is credited to Russell L. Reichert.
United States Patent |
5,592,969 |
Reichert |
January 14, 1997 |
Turbulence arrester
Abstract
A turbulence arrester is disclosed which allows fuel delivery at
rates equal to or approaching the rates achieved when using an open
ended drop tube. The turbulence arrester has a large number of
small apertures around its circumferential surface. Fuel flow
streams through these apertures contract a short distance from the
orifice, then expand and interfere with fuel flow streams from
adjacent apertures to generate eddies and turbulence. The
turbulence is substantially confined to a narrow region surrounding
the turbulence arrester.
Inventors: |
Reichert; Russell L.
(Bellville, TX) |
Family
ID: |
23589906 |
Appl.
No.: |
08/401,944 |
Filed: |
March 10, 1995 |
Current U.S.
Class: |
137/592;
137/561A |
Current CPC
Class: |
F15D
1/001 (20130101); F15D 1/08 (20130101); Y10T
137/86372 (20150401); Y10T 137/85938 (20150401) |
Current International
Class: |
F15D
1/00 (20060101); F15D 1/08 (20060101); F16K
051/00 () |
Field of
Search: |
;137/561A,592 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Look; Edward K.
Assistant Examiner: Lee; Michael S.
Attorney, Agent or Firm: Rosenblatt & Redano, P.C.
Claims
I claim:
1. A turbulence arrester for a storage tank drop tube
comprising:
a body having an open end for connection to the drop tube;
a closed end; and
a wall therebetween, said wall having a plurality of baffleless
apertures permitting liquid flow therethrough, said apertures sized
and spaced so that turbulence liquid flow through said apertures is
confined to a region approximately two drop tube diameters from the
wall.
2. The turbulence arrester of claim 1 wherein said aperture has an
area, said open end has a cross-sectional area, and the combined
area of said apertures exceeds the cross-sectional area of said
open end.
3. The turbulence arrester of claim 2 wherein the combined area of
said apertures exceeds the cross-sectional area of said open end by
a ratio of at least 4:1.
4. The turbulence arrester of claim 1 wherein said body is made of
carbon steel.
5. The turbulence arrester of claim 1 further comprising an adapter
connecting said open end to said drop tube.
6. A turbulence arrester for a storage tank drop tube
comprising:
a striker plate; and
a strainer having a first end connected to said drop tube and a
second end abutting said striker plate, said strainer including a
plurality of apertures permitting liquid flow therethrough, said
apertures sized and spaced so that turbulence in liquid flow
through said apertures is confined to a region approximately two
drop tube diameters from the wall.
7. The turbulence arrester of claim 6 wherein each said aperture
has an area, said basket strainer has a cross-sectional area, and
the combined area of said apertures exceeds the cross-sectional
area of said basket strainer.
8. The turbulence arrester of claim 7 further comprising an adapter
connecting said second end to a drop tube.
9. The turbulence arrester of claim 7, wherein each said aperture
has an area, said open end has a cross-sectional area and the
combined area of said apertures exceeds the cross-sectional area of
said open end.
10. The turbulence arrester of claim 9, wherein the combined area
of apertures exceeds the cross-sectional area of said open end by a
ratio of at least 4:1.
11. The turbulence arrester of claim 10, wherein said body is made
of carbon steel.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to underground storage tanks, and
particularly to turbulence arresters on drop tubes used to fill
underground storage tanks.
2. Background of the Invention
In the United States alone there are approximately five million
underground storage tanks used to fuel autos, trucks, planes, etc.
Sediment and debris from fuel deliveries or from the tank itself
(due to rust, scaling, etc.) accumulate at the bottom of these
tanks. Undisturbed, these contaminants would lie on the bottom of
the tank and cause no problems. Unfortunately fuel delivery to the
tank, which is typically by way of a drop tube installed in the
tank, disturbs these contaminants. Therefore fuel filters must be
used when dispensing the fuel from the tank. Over time these
filters will accumulate deposits of the contaminants and will clog.
No fuel can be dispensed from the tank until the filter is changed,
an expensive process which disrupts operations for extended periods
of time.
Certain fuels, such as diesel, have a tendency to foam during fuel
drops. This foam must dissipate before fuel levels in the tank may
be accurately read to verify the amount of fuel dropped. Tank
owners generally must pay for time spent by delivery persons
waiting for the foam to dissipate.
Many underground storage tanks are equipped with continuous in-tank
monitors which sound an alarm when water is detected. When water
accumulations at the bottom of the tank are disturbed during fuel
drops, the alarm may sound unnecessarily.
Known turbulence arresters utilize various arrangements of baffles
to slow the fuel's flow velocity as it exits the drop tube. The
fuel dispersed into the tank thus produces less turbulence in the
fuel already present in the tank and is therefore less likely to
disturb contaminants. Such arrangements also impede the delivery of
fuel to the tank, thus requiring longer to complete the fuel
drop.
SUMMARY OF THE INVENTION
A turbulence arrester is disclosed which allows fuel delivery at
rates equal to or approaching the rates achieved when using an open
ended drop tube. The turbulence arrester has a large number of
small apertures around its circumferential surface. Fuel flow
streams through these apertures contract a short distance from the
orifice, then expand and interfere with fuel flow streams from
adjacent apertures to generate eddies and turbulence. The
turbulence is substantially confined to a narrow region surrounding
the turbulence arrester.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an axial view of an underground storage tank.
FIG. 2 is a side view of a drop tube fitted with a turbulence
arrester according the present invention.
FIGS. 3a an 3b are detailed side views of the present
invention.
FIG. 4 is a diagram of the pressure in a fluid stream exiting an
aperture as a function of distance from the aperture.
FIG. 5 is a diagram of the contraction experienced by a fluid
stream exiting an aperture.
FIG. 6 is an illustration of the arrangement of perforations which
may be used with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Underground storage tanks 10 are generally equipped with a fill
riser 12 and a drop tube 14. The turbulence arrester 20 of the
present invention is fitted to the end of the drop tube 28. The
turbulence arrester 38 may be fitted directly to drop tube by means
of an appropriate adapter 38.
The turbulence arrester has a vertical basket strainer 32 resting
on a striker plate 30 to form an annular body having one closed
end. The surface of the basket strainer, which forms the
circumferential surface of the turbulence arrester, is a thin plate
which includes a large number of squared-edged apertures or
orifices 33. The apertures must be sufficient in size and number so
that fuel flow rates into the tank are not impeded, but should be
small and closely spaced together so that flow streams through
adjacent apertures will mix and interfere within a short distance
from the basket strainer. The combined area of the apertures should
exceed the cross-sectional area of the drop tube by several
multiples. For example, an arrester with a diameter of 3.45", an
effective length of 14", and 0.045" apertures placed on 0.066"
straight centers will have in excess of 34,000 apertures. The
combined area of these apertures exceeds the cross-sectional area
of a 4" diameter drop tube by a factor of over four. This
arrangement confines turbulence to a region of approximately two
drop tube diameters from the surface of the arrester.
In the presently preferred embodiment, both the basket strainer and
the striker plate are formed of carbon steel, with the bottom of
the turbulence arrester encapsulated in known epoxy formulated for
gasoline immersion. However any material compatible with the stored
liquid may be used, including stainless steel or an alloy.
In operation, fuel descending through the drop tube encounters the
striker plate 30 and is forced through the circumferential
apertures 33. As fuel streams exit each orifice, they experience an
area of minimum pressure 40 downstream called the vena contracta,
which causes the fuel stream to contract D2. As the exiting fuel
stream enters the body of fuel already present in the tank, it
undergoes a change in velocity. The difference between the exiting
velocity V1 and the velocity downstream V2 is accompanied by a
corresponding change in pressure in the fuel stream. The fuel
stream therefore expands, generating friction between itself and
fuel streams from adjacent apertures. The adjacent fuel streams
thus begin to mix and interfere, creating eddies and turbulence.
However this turbulence is limited to a narrow region within the
tank surrounding the turbulence arrester, and becomes negligible
after a short distance, preferably less than two drop tube
diameters, from the apertures. Because the turbulence is restricted
to a region near the turbulence arrester, contaminants at the
bottom of the tank remain undisturbed and therefore are not picked
up by the submersible pump and transferred to the filter at the
dispenser. Moreover water accumulations near the bottom of the tank
will not unnecessarily cause monitors to sound an alarm. The
restriction of turbulence to a narrow region also inhibits foaming,
reduces vapor generation during the fuel drop, and reduces static
build-up associated with the fuel drop.
Many modifications and variations may be made in the embodiments
described herein and depicted in the accompanying drawings without
departing from the concept of the present invention. Accordingly,
it is clearly understood that the embodiments described and
depicted herein are illustrative only and are not intended as a
limitation upon the scope of the present invention.
* * * * *